A research team led by the Department of Energy’s Oak Ridge National Laboratory has found a way to thwart deactivation of catalysts for the dry reforming of methane. Dry reforming of methane converts methane and carbon dioxide into syngas, a valued mixture of hydrogen and carbon monoxide used by oil and chemical companies worldwide. An open-access paper on their work is published in Nature Communications. The team has applied for a patent for their invention as a way to minimize catalytic deactivation.

Improving the catalyst that speeds syngas production could have enormous impact on global energy security, cleaner fuels and chemical feedstocks. In countries lacking oil reserves, syngas derived from coal or natural gas is critical for making diesel and gasoline fuels. Moreover, syngas components can be used to make other commodity chemicals.

Hydrogen, for example, can be used as a clean fuel or as a feedstock for ammonia to create fertilizer. Methanol, an alcohol that can be made from syngas, is a source of ingredients for producing plastics, synthetic fabrics and pharmaceuticals. Methanol is also a good carrier of hydrogen, which is hard to pressurize and dangerous to transport. As the simplest alcohol, methanol contains the highest ratio of hydrogen to carbon; it can be safely transported and converted to hydrogen at the destination.

This [dry reforming of methane] reaction sounds attractive because you are converting two greenhouse gases into a valuable mixture. However, the issue for decades has been that the catalysts required to carry out this reaction deactivate quickly under reaction conditions, making this reaction nonviable on an industrial scale.

—ORNL’s Felipe Polo-Garzon

To attain significant conversion of reactants, the reaction must be conducted at temperatures greater than 650 degrees Celsius, or 1,200 degrees Fahrenheit.

At this high temperature, the catalysts undergo two deactivation processes. One is sintering, in which you lose surface sites that undertake the reaction. The other is the formation of coke—basically solid carbon that blocks the catalyst from contacting the reactants.

—Felipe Polo-Garzon

Catalysts work by providing a large surface area for reactions. Metal atoms such as nickel have electronic properties that allow them to temporarily bind reactants, making chemical bonds easier to break and create. Sintering causes nickel particles to clump, reducing the surface area available for chemical reactions. Likewise, coking chokes a catalyst.

During the reaction on the catalyst surface, methane will lose its hydrogen atoms one by one until only its one carbon atom is left. If no oxygen bonds to it, leftover carbon will aggregate on the catalyst’s nickel surface, covering its active face. This coking deposition causes deactivation. It is extremely common in thermal catalysis for hydrocarbon conversion.

—ORNL’s Junyan Zhang

Today, most commercial syngas is made by steam reforming of methane, a process that requires large amounts of water and heat and that also produces carbon dioxide. By contrast, dry reforming of methane requires no water and actually consumes carbon dioxide and methane.

By tuning interactions between the metal active sites and the support during catalyst synthesis, the scientists suppressed coke formation and metal sintering. The new catalyst provides outstanding performance for dry reforming of methane with extremely slow deactivation.

The novel catalyst consists of a zeolite that contains silicon, aluminum, oxygen and nickel. The zeolite’s supportive framework stabilizes the metal active sites. To synthesize the zeolite catalyst, the researchers remove some atoms of aluminum and replace them with nickel.

Next, the researchers will develop other catalyst formulations for the dry reforming of methane reaction that are stable under a broad range of conditions.

We’re looking for alternative ways to excite the reactant molecules to break thermodynamic constraints. We relied on rational design, not trial and error, to make the catalyst better. We’re not just developing one catalyst. We are developing design principles to stabilize catalysts for a broad range of industrial processes. It requires a fundamental understanding of the implications of synthesis protocols. For industry, that’s important because rather than presenting a dead-end road in which you try something, see how it performs, and then decide where to go from there, we’re providing an avenue to move forward.

—Felipe Polo-Garzon

The DOE Office of Science funded the research. The work relied on several DOE Office of Science user facilities: the CNMS at ORNL; the Center for Functional Nanomaterials and the National Synchrotron Light Source II, both at Brookhaven; the Stanford Synchrotron Radiation Lightsource at SLAC and the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory.

Resources

• Zhang, J., Li, Y., Song, H. et al. Tuning metal-support interactions in nickel–zeolite catalysts leads to enhanced stability during dry reforming of methane. Nat Commun 15, 8566 (2024). doi: 10.1038/s41467-024-50729-8